Re: [PATCH 1/4] perf: Add memory load/store events generic code

[Paul Mackerras <paulus@samba.org>]

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On Tue, Jul 05, 2011 at 02:03:38PM +0200, Peter Zijlstra wrote:
> On Mon, 2011-07-04 at 10:44 +0200, Peter Zijlstra wrote:
> > Anton, Paulus, IIRC PowerPC had some sort of Data-Source indication,
> > would you have some docs available on the PowerPC PMU?
> 
> Going through
> http://www.power.org/resources/downloads/PowerISA_V2.06B_V2_PUBLIC.pdf
> 
> Book III-S, Appendix B
> 
> I can only find the SDAR thing (which I assume is what PERF_SAMPLE_DATA
> uses) but no mention of extra bits describing where the data was sourced
> from. For some reason I had the impression PPC64 had the capability to
> tell if a load/store was from/to L1/2/3/DRAM etc.
> 
> Now since the above document is in fact not an exhaustive spec of a
> particular chip but more an outline of what a regular ppc64 chip should
> have, with lots of room for implementation specific extensions it
> doesn't say much at all.
> 
> So do you know of such a feature for PPC64 and if so, where's the
> docs? :-)

Unfortunately the P7 PMU documentation is not available publicly yet. :(

There are events that can be used to count how many times data or
instructions get loaded from different places in the memory
subsystem.  There are 15 separate DATA_FROM_xxx events, for instance,
that count things like "number of times data was loaded from L2 or L3
cache on another chip and the cache line was in shared state".
They're great if you want fine detail on memory traffic but perhaps
not so good if you want a broad overview (there are separate events
for L1 and L2 accesses and misses though).

I've attached a table of P7 PMU events.  Look for the PM_DATA_FROM_xxx
and PM_INST_FROM_xxx events.

Paul.

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